Analysis of the pilot SGMACE: French report
In February 2011, Interbull ran a SGMACE and a MACE including only country that provided GEBVs. We compared the SGMACE results with the MACE results and with the french domestic GEBVs. We analysed protein yield, somatic cell score (SCS), stature and fertility (CC1) only for bulls having genomic information. The study showed expected results such as high correlations, increased reliabilities and no mean difference between MACE and SGMACE proofs, excepted in few cases. However, the variability of SGMACE-GEBVs for stature and SCS highly decreased compared to EBVs, which was not explained and which may suggest differences between domestic GEBVs and EBVs.
The study also showed the impact of genetic correlations between countries on SGMACE results. They affect the gain in accuracy between MACE and SGMACE; when they are available, French domestic GEBVs of foreign bulls are more reliable than SGMACE GEBVs, which also affected the variability of GEBVs.
At this stage, the benefit in SGMACE seems limited and more investigation is needed: closer analysis of consistency between EBVs and GEBVs sent by each country, analysis with all GEBVs (official and unofficial), and a new SGMACE pilot run may answer some questions.
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